HOMOGENIZATION OF NONDIVERGENCE-FORM ELLIPTIC EQUATIONS WITH DISCONTINUOUS COEFFICIENTS AND FINITE ELEMENT APPROXIMATION OF THE HOMOGENIZED PROBLEM.

We study the homogenization of the equation A(\cdot\varepsilon): D2u\varepsilon =f posed in a bounded convex domain Ω\subset Rn subject to a Dirichlet boundary condition and the numerical approximation of the corresponding homogenized problem, where the measurable, uniformly elliptic, periodic, and symmetric diffusion matrix A is merely assumed to be essentially bounded and (if n > 2) to satisfy the Cordes condition. In the first part, we show existence and uniqueness of an invariant measure by reducing to a Lax--Milgram-type problem, we obtain L2-bounds for periodic problems in doubledivergence-form, we prove homogenization under minimal regularity assumptions, and we generalize known corrector bounds and results on optimal convergence rates from the classical case of H\"older continuous coefficients to the present case. In the second part, we suggest and rigorously analyze an approximation scheme for the effective coefficient matrix and the solution to the homogenized problem based on a finite element method for the approximation of the invariant measure, and we demonstrate the performance of the scheme through numerical experiments. [ABSTRACT FROM AUTHOR]